3-phase motor driver # BA6870S Technical Documentation
*Manufacturer: ROHM Semiconductor*
## 1. Application Scenarios
### Typical Use Cases
The BA6870S is a specialized 3-phase brushless DC motor driver IC primarily designed for precision motor control applications. Its typical use cases include:
- Spindle motor drives for optical disc systems (CD/DVD/Blu-ray drives)
- Cooling fan controllers in computing equipment and servers
- Precision positioning systems requiring smooth rotation control
- Small appliance motors requiring variable speed control
- Industrial automation where precise motor speed regulation is critical
### Industry Applications
Consumer Electronics:
- Optical disc drives in home entertainment systems
- Computer cooling systems and server fans
- Office automation equipment (printers, scanners)
Industrial Sector:
- Small industrial automation equipment
- Laboratory instrumentation requiring precise motion control
- Medical device motor control systems
Automotive:
- Automotive HVAC blower controls
- Precision motor systems in infotainment units
### Practical Advantages and Limitations
Advantages:
- Integrated design reduces external component count and PCB space requirements
- Built-in protection circuits including thermal shutdown and overcurrent protection
- Low power consumption in standby mode (typically <10μA)
- Wide operating voltage range (4.5V to 15V) accommodates various power supply configurations
- Soft switching technology minimizes electromagnetic interference (EMI)
Limitations:
- Current handling capacity limited to approximately 1.5A peak current
- Heat dissipation requires proper thermal management in continuous high-load applications
- Limited to 3-phase brushless DC motors only, not suitable for other motor types
- Requires external Hall sensors for position detection
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Inadequate Heat Management
- Problem: Overheating during continuous operation at maximum current
- Solution: Implement proper heatsinking and ensure adequate airflow; use thermal vias in PCB design
Pitfall 2: EMI Issues
- Problem: Electromagnetic interference affecting nearby sensitive circuits
- Solution: Implement proper filtering capacitors and follow recommended PCB layout practices
Pitfall 3: Motor Start-up Failures
- Problem: Difficulty starting under high load conditions
- Solution: Implement soft-start circuitry and ensure proper current limiting settings
### Compatibility Issues with Other Components
Hall Sensor Compatibility:
- Requires digital Hall sensors with open-drain output
- Compatible with most industry-standard Hall effect sensors (e.g., Allegro A3144, Honeywell SS41)
- Ensure proper sensor placement with 120° electrical spacing for optimal performance
Microcontroller Interface:
- Compatible with 3.3V and 5V logic levels
- Requires proper level shifting if interfacing with lower voltage microcontrollers
- PWM input compatible with standard microcontroller outputs
Power Supply Requirements:
- Decoupling capacitors (100nF ceramic + 10μF electrolytic) required near power pins
- Separate analog and digital grounds recommended for noise-sensitive applications
### PCB Layout Recommendations
Power Stage Layout:
- Use wide traces for motor power paths (minimum 2mm width for 1A current)
- Place bulk capacitors (100μF) close to motor power inputs
- Implement star grounding for power and signal grounds
Signal Integrity:
- Route Hall sensor signals as differential pairs where possible
- Keep PWM control lines away from high-current motor traces
- Use ground planes beneath sensitive analog sections
Thermal Management:
- Include
